Particulate matter air pollution (PM) has been linked with chronic respiratory diseases. Real-life exposures are likely to involve a mixture of chemical and microbial stimuli, yet little attention has been paid to the potential interactions between PM components (e.g., Ni) and microbial agents on the development of inflammatory-like conditions in the lung. Using the Toll-like receptor (TLR)-2 agonist MALP-2 as a lipopeptide relevant to microbial colonization, we hypothesized that nickel sensitizes human lung fibroblasts (HLF) for microbial-driven chemokine release through modulation of TLR signaling pathways. NiSO(4) (200 muM) synergistically enhanced CXCL8, yet antagonized CXCL10 mRNA expression and protein release from HLF in response to MALP-2. RT(2)-PCR pathway-focused array results indicated that NiSO(4) exposure did not alter the expression of TLRs or their downstream signaling mediators, yet significantly increased the expression of cyclooxygenase 2 (COX-2). Moreover, when NiSO(4) was given in combination with MALP-2, there was an amplified induction of COX-2 mRNA and protein along with its metabolic product, PGE2, in HLF. The COX-2 inhibitor, NS-398, attenuated NiSO(4) and MALP-2-induced PGE2 and CXCL8 release and partially reversed the NiSO(4)-dependent inhibition of MALP-2-induced CXCL10 release from HLF. These data indicate that NiSO(4) alters the pattern of TLR-2-dependent chemokine release from HLF via a COX-2-mediated pathway. The quantitative and qualitative effects of NiSO(4) on microbial-driven chemokine release from HLF shed new light on how PM-derived metals can exacerbate respiratory diseases.